One prior art, lever operated, sheet dispenser wherein the sheet material is dispensed through a nip formed by a drive roller and a pressure roller is described in U.S. Pat. No. 3,459,353-Taylor. In Taylor, a manually operated lever and a toothed quadrant member have a common center of rotation. The drive roller has a shaft to which is attached a gear that is driven by the quadrant member. Interposed between the gear and the drive roller is a one-way clutch mechanism which allows the rotational motion of the gear to be transmitted to the drive roller for only one direction of rotation of the gear. Since the sheet is dispensed when the lever travels in one direction and is not dispensed when the lever travels in the other direction, it is generally necessary to use a drive roller that has a relatively large diameter in order to dispense a desired length of the material for a single operation of the lever. Since the force applied to the lever must overcome the force applied to the drive roller by the pressure roller, it would be desirable to employ a drive roller with a relatively smaller diameter and to increase the angular rotation of the drive roller during a single operation of the lever in order to dispense the desired length of the sheet material.
One prior art approach for increasing the angular rotation of a drive roller in a lever operated dispenser is described in U.S. Pat. No. 3,606,125-Tucker et al. Tucker et al discloses a towel dispenser in which a manually-operated lever and a pair of toothed quadrant members all have the same center of rotation. The drive roller shaft has attached thereto first and second gears, one of the gears being driven by one quadrant member when the lever travels in one direction and the other gear being driven by the other quadrant member when the lever travels in the other direction so as to dispense toweling during both the advance and return strokes of the lever.
Other lever-operated towel dispensers that employ a gear driven drive roller are described in U.S. Pat. Nos. 1,229,533-Shattuck and 3,107,957-Batlas et al. In those patents the gear means are driven by a pawl and ratchet assembly which limits the drive roller to a single direction of rotation.
There is another advantage to having the lever rotate through a relatively small angle in order to dispense a desired length of toweling. If the lever must rotate through a very large angle, then the lever must either be mounted on the side of the cabinet, or if mounted on the front of the cabinet may prove to be too cumbersome during operation or servicing of the cabinet. If the lever rotates through a small angle, it can be mounted so that only the end of the lever projects through the front wall of the dispenser.
Lever-operated dispensers generally employ some type of spring means for returning the lever to a starting position. As the lever is moved away from the starting position, the force of the return spring acting on the lever increases with the distance of the lever from the starting position. It would, therefore, be desirable to have the mechanical advantage of the feed roller drive mechanism increase as the lever moves away from the starting position which would, at least in part, compensate for the increased force on the lever resulting from the return spring.